A C++ program to fill polygon using Flood fill algorithm


#include<graphics.h>
#include<iostream.h>
#include<conio.h>
#include<math.h>
//————————Function Prototypes———————–//
void Flood_fill(const int,const int,const int,const int);
void Polygon(const int,const int []);
void Line(const int,const int,const int,const int);
int main(){
int gd=DETECT,gm;
initgraph(&gd,&gm,””);
int polygon_points[14]={365,325, 400,290, 450,290, 485,325, 450,360,
400,360, 365,325};
setcolor(15);
Polygon(7,polygon_points);
Flood_fill(425,325,12,0);
setcolor(15);
settextstyle(0,0,1);
outtextxy(395,370,”Polygon”);
getch();
return 0;}
//——————— Flood-Fill() ———————–//
void Flood_fill(const int x,const int y,const int fill_color,const int old_color){
if(getpixel(x,y)==old_color){
putpixel(x,y,fill_color);
Flood_fill((x+1),y,fill_color,old_color);
Flood_fill((x-1),y,fill_color,old_color);
Flood_fill(x,(y+1),fill_color,old_color);
Flood_fill(x,(y-1),fill_color,old_color);
}}
//——————— Polygon() ————————//
void Polygon(const int n,const int coordinates[]){
if(n>=2) {
Line(coordinates[0],coordinates[1],coordinates[2],coordinates[3]);
for(int count=1;count<(n-1);count++)
Line(coordinates[(count*2)],coordinates[((count*2)+1)],coordinates[((count+
1)*2)],coordinates[(((count+1)*2)+1)]);
}}
//——————– Line() —————————//
void Line(const int x_1,const int y_1,const int x_2,const int y_2){
int color=getcolor();
int x1=x_1;
int y1=y_1;
int x2=x_2;
int y2=y_2;
if(x_1>x_2){
x1=x_2;
y1=y_2;
x2=x_1;
y2=y_1; }
int dx=abs(x2-x1);
int dy=abs(y2-y1);
int inc_dec=((y2>=y1)?1:-1);
if(dx>dy) {
int two_dy=(2*dy);
int two_dy_dx=(2*(dy-dx));
int p=((2*dy)-dx);
int x=x1;
int y=y1;
putpixel(x,y,color);
while(x<x2) {
x++;
if(p<0)
p+=two_dy;
else {
y+=inc_dec;
p+=two_dy_dx; }
putpixel(x,y,color); } }
else {
int two_dx=(2*dx);
int two_dx_dy=(2*(dx-dy));
int p=((2*dx)-dy);
int x=x1;
int y=y1;
putpixel(x,y,color);
while(y!=y2){
y+=inc_dec;
if(p<0)
p+=two_dx;
else
{
x++;
p+=two_dx_dy;
}
putpixel(x,y,color);
}
}
}